1. Field of the Invention
The present invention relates to a sheet conveying device, an image forming apparatus, and a sheet thickness detection system.
2. Description of the Related Art
Image forming apparatuses such as printers and copiers convey a sheet that is a recording medium and forms an image on the sheet surface. Such an image forming apparatus includes a technology for detecting a double feeding state where plural sheets stacked on top of each other are conveyed together, and a technology for detecting the thickness of the sheet when conveying the sheet for optimizing image forming conditions according to the sheet thickness.
In an electrophotographic image forming apparatus, by detecting the sheet thickness, for example, the transfer conditions and fixing conditions are optimized according to the sheet thickness, and therefore the image quality can be improved.
As a technology for detecting the sheet thickness, for example, patent document 1 proposes the following medium thickness detecting device. The medium thickness detecting device includes a driving member positioned in a conveying path of a medium for rotationally driving the medium; a contact rotating body positioned to face the driving member, which can contact the medium being conveyed and move in the thickness direction of the medium according to the thickness of the medium when contacting the medium; and a movement amount detecting unit for detecting the movement amount of the contact rotating body in the thickness direction. The medium thickness is detected based on the movement amount between when the contact rotating body is contacting the medium and when the contact rotating body is not contacting the medium. Thus, even within a short time period for detecting the thickness of the medium, the thickness of the medium can be detected with high precision.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2011-37585
However, in the medium thickness detecting device of patent document 1, the contact rotating body, the mechanism by which the contact rotating body can be moved in the thickness direction of the medium, and the sensor for detecting the movement amount of the contact rotating body needs to be provided separately from the mechanism for conveying the medium. Therefore, the configuration may be complex.